Why a half ACME client?

It's not 'half' a client to only support a subset of all possible challenge types, as the HTTP-01 and DNS-01 challenges in particular cover wildly different use cases which are differently convenient for different scenarios.

DNS-01 is require for wildcard certificates which is a common need, it's entirely standalone and detached from your webserver configuration, and it broadly needs to integrate to whatever proprietary API for TXT records your DNS registrar of choice uses; so as a result there's a lot of registrar-specific ACME clients. Are all those only 'half' an ACME client since they don't support HTTP-01 challenges?